Arrangement for amplitude regulation



Patented July 14, 1942 ARRANGEMENT FR AMPLITUDE y REGULATION Hans-Joachim Bertram and Karl vHeinz Hofmann, Berlin, Germany, assignors to C. Lorenz Aktiengesellschaft, 'Berlin-Tempelhof,

man y, al Company Ger- Application-June 28, 1939, kSerial No. 281,538 In Germany June 28, 1938 1 Claim.

The amplitude regulation in high frequency or low frequency circuits is in general such that the regulating voltage, in dependence on which the amplitude regulation of an amplifier, for instance, is to be effected, is rectified and that the uni-directional voltage so obtained is made to form the grid bias for an amplifying tube or a number thereof. By varying the regulating voltage the grid bias of the regulating tube is varied, the working point of this tube being displaced into the region of greater or less slope of the characteristic curve.

Regulating arrangements of this type, however, have the drawback that the working point of the amplifying tubes is not invariably located in the linear part of the characteristic curve but is by the regulating voltage displacedfalso into the curvature thereof. The amplification is hence not effected in llinear fashion. As a result, distortions arise especially in the region oi'y smaller amplitudes. Furthermore, in the case of high frequency currents there is the disadvantage that the amplituderegulation entails a variation of the tube resistance and thereby causes the appertaining oscillatory circuits to be det-uned.

f In order to overcome these drawbacks the invention described hereafter is concerned with a regulating arrangement which is quite different from` those of the aforesaid kind. In the novel arrangementv the working point of the amplifying tubes is stationary andv a countercoupling, that is to say, a negative reaction coupling over an electron tube is provided. The

linternal resistance of this countercoupling tube is" controlled in dependence upon the regulating voltage, whereby the countercoupling is rendered )more or less tight. As in the case of a tight countercoupling, that is, with low resistance of the countercouplng tube the loudness greatly decreases while increasing with the countercoupling becoming less tight, an amplitude regulation may be effected inl this way. The countercoupling tubemay be controlled inone way or another.

"age may be age soobtained may be usedas grid bias'. How- For instance, the regulating voltrectifled and the continuous volt-` ever, the countercoupling tube may be controlled instead by influencing its anode circuit.

The accompanying drawing shows in Figure 1 a diagram illustrating one embodiment of the invention as applied to an amplifier tube and in Figure 2 the invention is applied to an oscillation generator. i

The example shown in `Figure 1 has an amact on the grid vcircuit of tube I.

(Cl. NS2-171.5)

plifying tube or valve amplifier I to the grid circuit .of which the voltage to be amplified isA rived over a transformer 5 and terminals 6, 1.

It is immaterial of course whether the described amplifyingarrangement is a low frequency amplifier or a high frequency amplifier.

In accordance with the invention an electron tube 8 is interposed between the anode circuit and grid circuit of tube I. The tube 8 causes the current flowing in this anode circuit to re- The feedback phase has to be so adjustedthat it shall be in opposition to the phase of a feedback used for the purpose of self-excitation. In the circuit of tube 8 a condenser 9 may be included. Also, an additional resistance I3 may be arranged in a mannerv to form a potentiometerl connection.

Assume the amplifier regulation to be effected in dependence upon the amplified voltage itself in order that `the output voltage of the amplifying tube I be always the same irrespective of the input voltage. To such end this output voltage is derived over a secondsecondary winding I0 of transformer 5 and is rectified by a rectifier II, and further. the uni-directional voltage so obtained is used as grid bias lforthe countercoupling tube 8. Such uni-directional or continuous voltage is effective over a resistance IZ.` 'I'he rectifier II is so connected that with the amplitude increasing in the anode. circuit of tube I the grid voltage of tube 8 will be displaced farther in the positive direction, the4 the loudness is hence decreased.

'I'he arrangement may of course be such that the control action will occur in the vreverse direction, thus entailing a so-called dynamics slope increase. In this case, the polarity o f the rectifier II has to be changed, and an amplitude increase in the anode circuit of tube I then causes the resistance oi' `tube 8 to increase so that the amplitude will be still farther enlarged.

The novel arrangement is not restricted to the regulation of amplifiers but may be employed also inrconnection with oscillation' generators, such as tube buzzers or high frequency transmitters, for example. In the ca-se of 'arrangements of the latter kind the amplitude of the oscillation produced by the generator may be a mannerl to effect modulation. For instance, in

Figure 2 the tube I is connected to act as a self-oscillation generator, and continuous current impulses in the shape of Morse signals supplied from a source MS are conducted to the grid of the countercoupling tube 8 interposed between the anode circuit and grid circuit o the oscillator tube, then a keying operation acting on the transmitter is eiected. By supplying an alternating voltage from source MS a modulation will be obtained.

What is claimed is:

A modulating arrangement comprising a rst electronA tube having an anode, a cathode and a grid,'said first tube being connected in a selfoscillation circuit including an output circuit .operatively connected to the anode of the rst tube, a second electron tube having an anode, a cathode, and a grid, the anodes of said tubes being connected together, a negative feed-back circuit between the anode and grid of said rst tube including a connection between the cathode of the second tube and the grid of the rst tube, means for producing a bias voltage proportional to the amplitude of the oscillatory energy in said output circuit, means for coupling said bias voltage means to the grid of said second tube in a positive sense, whereby an increase in the amplitude of the oscillatory energy in the output circuitvof said rst tube increases the bias voltage of the grid of said second tube positively, a source of modulating signals, and means for coupling said source of modulating signals to HANS-JOACHIM BERTRAM.

KARL IHIINZ HOFMANN. 

